// 追加

const fs = require('fs')
// fs.appendFile('../files/4.txt',"I'm good!!",{},err=> console.log(err))
// fs.appendFile('../files/4.txt',"I'm good!!",'utf8',err=> console.log(err))
fs.appendFile('../files/4.txt',"\nI'm all right.",{},(err)=> {
    if(err) console.log(err)
})